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Volume 44, Issue 2
Displaying 1-17 of 17 articles from this issue
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Shinji Takayama, Tetsu Oi1980 Volume 44 Issue 2 Pages 113-117
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSProcessing conditions of Fe40Ni40B20 metallic glassy ribbon, 10 mm in width, have been investigated by employing a single roll-casting method. To explore the conditions, the temperature of the melt, the angular velocity of the roll, and the ejection pressure of the melt were varied in turn while holding the other quenching parameters constant.
The thickness of the as-quenched glassy ribbon increases monotonically with increasing ejection pressure and decreases monotonically with increasing roll speed.
A mathematical treatment of the conditions for obtaining the good quality glassy ribbon has been attempted, and the result shows good accord with the present experimental data.View full abstractDownload PDF (509K) -
Etsuo Otsuki, Yoshimichi Masuda1980 Volume 44 Issue 2 Pages 117-123
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe crack path in cemented tungsten carbides has been investigated by means of ion microanalysis of the phase composition of the fracture surface and measurement of cracktip displacement using SEM. The result obtained are as follows:
(1) Cobalt content in the fracture surface of all the alloys investigated, is always over the nominal content in these alloys.
(2) The phase composition of the fracture surface changes with grain size of carbide in the alloy; for the fine grain cemented carbides, having a mean carbide intercept of 0.5 μm, it is about WC-42∼50 vol%Co irrespective of the alloy composition, and for the coarse grain cemented carbides, having a mean carbide intercept of 3.3 μm, the Co content in the fracture surface increases with the Co content.
(3) The crack path of the fine grain cemented carbides runs preferentially through the WC-Co interface, and coarse grain alloys break down by ductile fracture of the Co phase and brittle fracture of the WC-Co interface and the WC grain.
(4) Such a variation of the crack path depends on whether or not the size of WC the grain is larger than the locally yielded area around the crack tip; when the locally yielded area around the crack tip is larger than the WC grain size, the fracture in a mode of the fine grain alloy occurs, and if the dimensional relation is reversed, it turns out to be a type of the coarse grain alloy.View full abstractDownload PDF (660K) -
Kanji Masui, Mizuki Tachihara, Toshio Yamada, Tokuzou Tsujimoto1980 Volume 44 Issue 2 Pages 124-131
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSPhase-separation behavior of the Ni-P amorphous alloys was studied by a differential scanning calorimeter (DSC), a transmission electron microscope (TEM), small-angle X-ray scattering (SAXS) and a magnetic balance. The phase separation occurs in the composition range of about 8∼12 wt% phosphorus prior to the crystallization. From the analyses of the SAXS data by Guinier’s approximation or Porod’s law, it is suggested that two types of phase separation take place during aging; Ni-9.4 wt%P alloy decomposes to an interconnected structure of a Ni-rich zone and a P-rich zone apparently by a mechanism of spinodal decomposition, while Ni-11.5 wt%P alloy forms fine particles (ca. 5∼10 nm) of fcc nickel in an amorphous matrix by a homogeneous nucleation and growth mechanism. The results of magnetizatin measurements also support the occurrence of two types of phase separation in the aged alloys. After the phase separation, the P-rich amorphous phase directly transforms to an equilibrium state by forming a stable Ni3P crystal.View full abstractDownload PDF (1251K) -
Harusige Tsubakino, Ryoichi Nozato1980 Volume 44 Issue 2 Pages 131-138
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDiscontinuous precipitation in Cu-Be 25 alloy and Cu-2 wt%Be-0.1 and 0.2 wt%Co alloys has been investigated by means of metallographic observations and micro-hardness measurements. The volume fraction of discontinuous precipitation cells, cell growth rate, number of cells per unit volume and interlamellar spacing have been determined by quantitative metallographic measurements in the specimens aged at temperatures from 473 to 823 K. The data are compared with those in Cu-Be binary alloy reported previously.
The results obtained are as follows: (1) The nucleation sites of cells are similar to those in the binary alloy. (2) Cell growth rate (G) decreases and interlamellar spacing (l) increases with ageing time remarkably after the linear growth rate of cells. These phenomena may be attributed to the influence of continuous precipitation on the cell growth. (3) G and 1⁄l which are considered not to be iufluenced by the continuous precipitation, decrease with increasing Co content but Gl2 remains almost constant. (4) Grain boundary diffusivities, obtained from the modified Turnbull theory, are in fair agreement with those in the binary alloy. Therefore, it can be concluded that the cell growth is controlled by grain boundary diffusion of Be. (5) The main effect of the Co addition upon the discontinuous precipitation in Cu-Be alloys is considered to be retardation of the cell growth by a presumably favoured continuous precipitation.View full abstractDownload PDF (953K) -
Shigenori Hori, Masanori Suzuki, Yasukazu Unigame1980 Volume 44 Issue 2 Pages 138-143
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe brittleness of iron containing 0.001∼0.44% carbon has been investigated by the charpy U-notch impact test at various temperature and tensile test at 77 K. Impurities (manganese, oxygen etc.) in the specimen, which influence the ductile-brittle transition temperature, were minimized.
In the charpy test, the shape of absorption energy vs temperature curves depended on the carbon content and the test temperature. The value of elongation in the tensile tests depended on the quenching temperature (Tq) after slow cooling from the austenizing temperature. The maximum elongation was obtained in the specimen quenched from the solvus temperature (Ts) of carbon in ferrite. When Tq>Ts, the intergranular fracture occurred, while in the case of Tq<Ts the cleavage fracture took place.
The transition temperature, in the charpy test, first rose remarkably with increasing carbon content, and then appeared to rise slightly for carbon contents above 0.013%, whereas the cleavage fracture in ferrite was more strongly dependent on the presence of cementite in the tensile test. The higher sensitivity in the tensile test may be seen due to a higher probability of the existense of the favorable cementite for cleavage fracture in the gauge length of the specimen.View full abstractDownload PDF (785K) -
Yoshinori Wakamatsu, Fumio Takaaze, Masami Onishi1980 Volume 44 Issue 2 Pages 144-151
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDiffusion couples of ε(Cu3Sn)-Cu were primarily annealed at 773 K and then the couples were followed by the second annealing at higher temperatures of 803, 823 and 843 K. At the first stage of the annealing, only one diffusion layer of δ(Cu31Sn8) could be found. At the second annealing a new phase layer of γ(Cu5Sn) appears. After the γ phase layer appears, the width of the δ phase layer decreases to a minimum, followed by its linear increase. The amount of decrease in width of the δ phase layer increases with increase in its initial width and in the ratio of growth rate coefficient of the γ phase to that of the δ phase. The growth rate of the γ phase layer decreases with annealing time. However, it does not follow the parabolic law even when the time in the law is taken to be zero at the time of appearance of the γ phase.
Growth curves of the phase layers calculated by use of Wagner’s equation for movements of the phase interface fit fairly well with the experimental curves. The behavior of the δ phase layer after formation of the γ phase could be explained by use of Wagner’s equation. Wagner’s equation, in general, may be considered to be useful not only for simulation but also growth kinetics of the successively formed phase layers.View full abstractDownload PDF (813K) -
Toshiyuki Aida, Yukio Honda, Shigehiko Yamamoto, Katsuhisa Usami1980 Volume 44 Issue 2 Pages 152-159
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThermionic emission, vapor pressure and surface characterization have been investigated for the BaB6 powder prepared by means of the borothermic reaction. The results are as follows:
(1) High thermionic emission current of the BaB6 powder depended largely on the surface structure.
(2) Emission current density and Ba vapor pressure at 1000°C showed relatively higher values, while at a high temperature above 1200°C, they were lowered. However, from those deteriorated properties, the initial values were recovered either by exposing to atmosphere or by introducing O2 gas in operation.
(3) A remarkable increase in the thermionic emission current and Ba vapor pressure results from the oxidizing layer which is easy to form on the surface of the BaB6 powder. In high temperature treatment, that layer was removed in a relatively short time, and then a clean surface of the BaB6 powder was obtained.
(4) The above-mentioned oxidizing layer is mainly composed of BaO and B activator. The BaCO3 layer on the surface which was formed in the inadequate conditions for preparing BaB6 powder and the introduction of CO2 gas during operation made the current density lower reversely.
(5) As long as O2 gas is supplied sufficiently to the BaB6 powder, high Ba vaporization occurrs and high thermionic emission is obtained.View full abstractDownload PDF (608K) -
Masamichi Miki, Shigenori Hori, Yoshitsugu Amano1980 Volume 44 Issue 2 Pages 160-169
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe effects of the addition of 0.1∼0.5 wt% of Ti, and 0.3 wt% of Co, Ni, Fe, Cd, Zn, Al, In, Mn, Cr or Si on the grain boundary reaction in Cu-2 wt%Be alloy on aging at 523 or 623 K after quenching from 1093 K were investigated simultaneously with the effects of these elements on the intragranular precipitation of γ′ phase by the quantitative metallographic method. Moreover, the effects of these elements on the grain growth of Cu-2%Be alloy at the solution treatment temperature where γ′ phase could not precipitate were examined in connection with the effects of these elements on the grain boundary reaction at aging temperature, and the mechanism that these elements suppressed the grain boundary reaction was proposed. The results obtained are as follows:
(1) In Cu-2%Be alloy, the nodule increased rapidly along with the hardening due to the precipitation of γ′ phase in the matrix and engulfed the matrix entirely. It is considered that the increase of the lattice strain in the matrix due to the precipitation of the γ′ phase also acts as a driving force for the nodule growth in this alloy.
(2) In the case of the addition of 0.1∼0.5 wt%Ti, the degree of the effect that this element suppressed the nodule growth in Cu-2%Be alloy increased with increase of the amount of addition. The addition of 0.3%Ti suppressed the nodule growth in nearly the same degree as the addition of 0.3% of Co or Ni. The addition of 0.5%Ti showed remarkable effect and almost entirely suppressed the nodule growth.
(3) The addition of In, Ni, Fe hastened the precipitation of γ′ phase in the matrix, on the other hand, the addition of Co, Mn, Cr, Ti delayed the precipitation of the γ′ phase. The elements which suppressed remarkably the nodule growth were In, Cd, Ni, Fe, Co, Mn and Ti. Therefore, it became clear that all the elements which were effective against the grain boundary reaction did not necessarily act to hasten the precipitation of the γ′ phase.
(4) The obvious quantitative correlations were found out between the effect of these elements on the grain growth in Cu-2%Be alloy at 1093 K and the effect of these elements on the nodule growth at the aging temperature of 523 or 623 K.
(5) It is considered from above facts that the mechanism that the nodule growth in Cu-2%Be alloy is suppressed by these additional elements is similar to the mechanism that the grain growth of this alloy at 1093 K is suppressed by these elements.View full abstractDownload PDF (1153K) -
Masamichi Miki, Takashi Kitayama, Yoshitsugu Amano1980 Volume 44 Issue 2 Pages 170-179
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSIn order to investigate the influence of aluminum addition on the intragranular precipitation and the grain boundary reaction in Cu-30%-0.5%Be alloy, Cu-30%Ni-0.5%Be alloys containing 0.2∼2%Al were aged isothermally at 773 or 873 K after water quenching from 1323 K, and hardness measurements, optical and electron microscopic observation, X-ray diffraction analysis were done for these alloys. The results obtained were as follows:
(1) The precipitation of γ′ phase in the matrix grain was retarded with increase in aluminum content.
(2) In the case of addition of small amount of aluminum, the mode of the nodule growth was similar to that of Cu-30%Ni-Be alloy. And the time of the beginning of the nodule growth was retarded with increase in aluminum content and the growth of the nodule was suppressed with increase in aluminum content.
(3) In the case of large additions of aluminum, the mode of the nodule growth became similar to that of Cu-30%Ni-Al alloy, and the time of the beginning of the nodule growth was shortened with increase in aluminum content and the nodule growth of each alloy was almost stopped at the early stage of aging.
(4) Three phases, γ phase (NiBe), α phase and θ phase ((Ni·Cu)3Al), were observed in the nodule. The θ phase was fibrous at the early stage of aging and changed to a granular shape with the progress of aging. With increase in aluminum content, the amount of θ phase in the nodule increased and the microstructure in the nodule became similar to that in the nodule of Cu-30%Ni-Al alloy.
(5) The hardness of the nodule increased with increasing amount of the θ phase in the nodule and decreased as the fibrous θ phase became granular during the aging.View full abstractDownload PDF (1477K) -
Masayuki Hasaka, Seiichi Ikeda1980 Volume 44 Issue 2 Pages 180-185
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSOrdering and phase separation in Fe-Al alloys have been investigated within the Bragg-Williams approximation. The tendencies of ordering and phase separation are proved to be caused by the effect of interactions between the 3rd or farther neighbouring atoms in addition to the 1st and 2nd ones. In Fe-Al alloys on the iron-rich side, three kinds of phase separation of α and B2, α and DO3, B2 and DO3 are demonstrated to occur besides the ordering of B2 and DO3 types. The equilibrium phase diagram of the Fe-Al system offered by the present calculation agrees well with previous experimental results.View full abstractDownload PDF (471K) -
Katsutoshi Ono, Kooichi Ishihara, Joichiro Moriyama1980 Volume 44 Issue 2 Pages 185-190
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe CaS-1 wt%Y2S3 solid electrolyte has been expected to be effective for thermodynamic studies of metal-sulfide systems. An acceptable solid-sulfide electrolyte must exhibit essentially complete ionic conductivity. The conductivity of the CaS-1 wt%Y2S3 solid solutions was determined by an a.c. bridge measurement-complex impedance plot combination method. Sulphur partial pressures were established by using metal-metal sulfide coexistence electrodes.
The isothermal conductivities were constant at a sulphur partial pressures lower than the equilibrium sulphur pressure of Cu-Cu2S coexistence and a gentle fall in conductivity was observed at the Ag-Ag2S equilibrium sulphur pressure. The result suggested that the conductivity of the CaS-1 wt%Y2S3 was ionic with the current carried by the Ca2+ ions via cationic vacancies. However, the conductivity value found in this study, 7.6×10−4 S/m at 1073 K for the CaS-1 wt%Y2S3 solid solution, is much smaller than the order of 10−1 S/m which has been obtained for the ZrO2-CaO, ThO2-Y2S3 and CaF2 solid electrolytes at the same temperature.View full abstractDownload PDF (492K) -
Masaru Yokota, Mototsugu Ohata, Hiroyasu Mitani1980 Volume 44 Issue 2 Pages 191-196
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe rate equation of penetration of liquids into porous bodies was introduced on the assumption that the laminar flow is dominant over the entire duration of the penetration process:
(This article is not displayable. Please see full text pdf.)
\ oindentand the solution of the above equation is given by;
(This article is not displayable. Please see full text pdf.)
\ oindentwhere the equilibrium height of penetration (h∞)=2γcosθ∞⁄Reρg, the tortuosity (Te)=6(1−p)sinθ⁄π(π⁄3<θ<π⁄2) and the shape factor (Ce)=Te⁄32, and the other symbol marks are; v, h and t: velosity, height at time t, p: porosity, Re: effective radius of capillary tubes, η, γ and ρ: the viscosity, the surface tension and the density of liquid, θ∞: the contact angle between solid and liquid, g: the gravitational acceleration, respectively.
From a comparison of the calculated values with the experimental ones, it has been confirmed that the above described solution is valid only for the penetration process into fully sintered porous bodies; i.e., for the case that the ratio of the diameter of necks between particles to that of powder particles is nearly equal to or not less than 0.5, where the turbulent flow is preferential at a very early stage of the penetration process. In the case of being less than this value it may be reasonable to suppose that the other resistant forces at the necks, due to local turbulence or adsorption, act on the motion of liquids in porous bodies.View full abstractDownload PDF (564K) -
Nobumasa Kemori, Iwao Katayama, Zensaku Kozuka1980 Volume 44 Issue 2 Pages 197-201
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSThe activity of oxygen in liquid Ni-Cu alloys was measured at 1733 K using solid oxide galvanic cells of the following type:
(This article is not displayable. Please see full text pdf.)
\ oindentBased on the above experimental results, the dependence of the activity coefficient of oxygen at infinite dilution on alloy composition was determined as follows:
(This article is not displayable. Please see full text pdf.)
Furthermore the following equation was derived as the influence of Cu addition on the activity coefficient of oxygen in liquid Ni:
(This article is not displayable. Please see full text pdf.)
\ oindentBy a comparison of the results obtained in this study with published data, the standard entropy change of solution of oxygen in liquid Ni-Cu alloys for the reaction: 1/2O2 (g, 101.325 kPa)→O (in liquid Ni-Cu alloys, NO=0.01) was found to be positive in the alloy composition range of XNi=1.0∼0.1.View full abstractDownload PDF (401K) -
Hisashi Kuwano, Yasuhiro Morooka1980 Volume 44 Issue 2 Pages 202-206
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSInternal magnetic fields of 57Fe nuclei have been measured to clarify a phase decomposition process and compositional fluctuations of an Fe-56 at%Cr alloy annealed in the temperature range 730∼1050 K, by means of the Mössbauer effect. The alloy spinodally decomposes into Fe-rich and Cr-rich solid solutions by aging below a critical temperature Tc, i.e., 830 K. In early stages of the decomposition, the solute atom concentration Ct at time t changes exponentially with the lapse of time, following Cahn’s spinodal equation:
(This article is not displayable. Please see full text pdf.)
\ oindentwhere C0, A, Rm are the initial average concentration, a constant and an amplification factor, respectively. Below Tc, it is found that the dependence of Rm on the aging temperature, T, is given by an empirical equation for the critical phenomena:
(This article is not displayable. Please see full text pdf.)
\ oindentwhere the critical index γ, is 1.3, and C is 60.3 K/min.
Mean internal fields increase by approximately 1.2 MA/m (15 kOe) during aging at temperatures just above Tc. The increase may be explained in terms of compositional fluctuations or clustering of like atoms in solid solutions, which is one of the features of the critical phenomena.View full abstractDownload PDF (403K) -
Hiroshi Nakai, Eiji Ataka, Toshiari Saegusa1980 Volume 44 Issue 2 Pages 207-214
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSWeight-gain of Co in corrosion by an Ar-SO2 mixtures was measured as a function of time at 873∼1273 K and the scale structure was examined by X-ray diffractometer, optical microscope, and EPMA. The effect of pre-oxidation on the corrosion was also studied.
At 873∼1123 K the reaction kinetics followed a parabolic rate law and the rate-limiting step was considered to be the outward diffusion of Co ion. The scale consisted of a mono-layer of CoO containing sulphide particles of Co9S8 and small amount of Co1−xS. At 1173 K the initial reaction rate was the maximum among the present experiments. The scale showed triple-layers including an inner layer of Co9S8. At 1223 K the reaction kinetics followed a linear rate law. The scale was a thick mono-layer of cobalt sulphide with many cobalt oxide particles. At 1273 K the reaction kinetics followed a parabolic rate law. The scale consisted of many grown-up CoO particles in the Co9S8 layer.
The weight-gain increased with temperature having a peak at around 1173∼1223 K and then decreased. The increasing trend was understood by an increase of the diffusivity of species, and the decreasing trend was attributed to a decrease of the driving force for sulphidation of Co.
Pre-oxidation decreased the amount of corrosion of Co to less than one tenth of that without pre-oxidation. The scale structure never showed sulphides at the scale surface. This effect was considered to be the same as that by an addition of oxygen to the present atmosphere.View full abstractDownload PDF (860K) -
Hideo Saito, Yoichi Ishida1980 Volume 44 Issue 2 Pages 215-219
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSGrain boundary diffusion of 119mSn and 51Cr in pure iron was investigated by micro-autoradiography. The grain boundary diffusion coefficient of 119mSn was 2.0×10−17 m2/s at 473 K and the apparent activation energy was 4.2×104 J/mol at temperatures between 473∼873 K. The boundary diffusion of 51Cr was detected at temperatures above 873 K. The diffusion coefficient was 8.0×10−15 m2/s at 873 K.
The boundary diffusion of tin is pronounced in some boundaries in agreement with the microprobe-AES results. The investigation using electron channeling pattern showed the distribution of the boundaries in the specimen is not very heterogeneous except with small angle and twin boundaries. It is found that the ordinary enhanced boundary diffusion of tin is decreased not only with coincidence boundaries of small Σ values but also with certain co-axial boundaries.View full abstractDownload PDF (474K) -
Tokuzou Tsujimoto1980 Volume 44 Issue 2 Pages 220-221
Published: 1980
Released on J-STAGE: April 04, 2008
JOURNAL FREE ACCESSDownload PDF (159K)
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